1. Field of the Invention
The present invention relates a method of obtaining objective metal by leaching and dissolving valuable metal in ore into aqueous solution, and in particular, relates to a method of separating and obtaining copper by leaching the copper in one of series of processes.
2. Description of the Related Art
Copper sulfide ore is generally subjected to a dry processing in which the copper sulfide ore is melted at a temperature more than 1000 degrees C, and impurity such as iron is fixed in a slag and separated from the copper sulfide ore. In the dry processing, noble metal is concentrated and obtained into purified copper sulfide (Cu2S) that is called copper matte and is manufactured with the melting process. With the method, sulfur in the copper sulfide ore is gasified into sulfur dioxide. Therefore, exhaust gas treatment is needed. And high temperature is needed in a purifying treatment after melting. This results in a plenty of consumption of fuel. Further, there is a problem that increase of impurity grade of the matte results in increase of cyclic material and treatment efficiency is reduced. And there is a problem that the treatment efficiency is reduced with respect to low copper-grade material because ratio of sulfur and copper in feedstock is limited.
In order to solve the problems such as the exhaust gas treatment, a plenty of consumption of fuel, or limitation with respect to impurity of feedstock and copper grade, there are being developed a variety of processes called wet processing in which copper sulfide ore is treated in aqueous solution.
Leaching technology with sulfuric acid is established in wet refining process of copper from copper ore. And a commercial scale plant using SX-EW method, in which solvent extraction and electrolytic winning are combined, is constructed and operated.
The leaching of copper with the sulfuric acid bath is, however, generally used for ore mainly composed of oxide ore and is used for only a selected sulfide ore, because the leaching has problems that the reaction thereof is slow and noble metal may not be obtained. The leaching of copper from copper concentrate having high copper grade caused by ore dressing is not in practical use, because the leaching has low copper-leaching rate and difficult obtainment of noble metal as well as slow reaction.
The above-mentioned wet processing needs high temperature and high pressure in order to enlarge the leaching rate of copper. The quality of obtained electrodeposited copper is degraded or a structure of an electrolytic bath for obtaining gets complex, if the copper-leaching-rate is enlarged with chloride solution.
Au Patent No. 669906 “Production of metals from minerals” (hereinafter referred to as Document 1) discloses a method of leaching copper from sulfide ore with chloride bath using chloride aqueous solution, as a method not performing high-temperature and high-pressure treatment. The method disclosed in Document 1 leaches copper as Cu+ from sulfide ore under air atmosphere with Cl—Br-based acid electrolytic solution including Cu2+ that is generated with electrolytic winning and has high oxidation-reduction potential. Thus Cu+ is obtained with electrolytic winning.
However, this method treats halide (halex such as BrCl2−) that is difficult to treat during leaching and is poisonous. The electrolytic winning of copper in chloride bath causes high cost because copper grade is low and refinement is needed. And, equipment gets complex, and controlling gets difficult.
CA Patent No. 1105410 “Method of obtaining copper from sulphurized concentrates” discloses a method of obtaining copper having high grade, in which copper concentrate is leached out in chloride bath, copper ion is extracted into organic solvent from the chloride bath with solvent extraction method, organic phase and aqueous phase are separated from each other, divalent copper extracted into the organic solvent is converted into copper sulfate when the organic phase is in touch with sulfuric acid, and the copper is obtained with conventional electrolytic winning with use of sulfuric acid bath. In the method, copper is extracted with air being blown into the chloride bath. Therefore, phase splitting is degraded because of air oxidation and deposition of iron in solvent, and loss of extract agent is caused by contamination of the extract agent into air. At the present time, the wet smelting process of copper with use of the chloride bath is not profitable in cost and administration, compared to another mine development process. This results in difficulty in grand-scale mine treatment process.